We recently had a project in which we had to migrate a SharePoint farm from Siteminder-Custom STS authentication to ADFS 3.0

Siteminder - is a SAML Single Sign on Solution used by my customer which will authentication a user against any of the ID provider(Enterprise directory in our case) and will send SAML 2.0 back to the trusted applications. Since SharePoint doesnt understand SAML 2.0, they have used a Custom STS built on Asp.net to do the transformation for SAML 2.0 to SAML 1.1 and send back the SAML claims to SharePoint.

When ADFS 3.0 was released and promised a very good support for App Model we decided to move away from Custom STS to ADFS 3.0. The ID provider remained same [ ED], Interface to ID provider remained same [ Siteminder R 12.5], just that we knocked off Custom STS and added ADFS 3.0 into the stack. Now ADFS will do the SAML Transformation for us.

Now coming back to the topic. When we migrated from Custom STS to ADFS, we had to migrate the existing users. As the Identity provider was same, we dont have any changes in the user's actual identity, it just the user name prefix which is changed. [ From "i:05.t|siteminder|testuser1" to "i:0e.t|adfs|testuser1"]

We did the migration in 2 steps.

Step1 : migrated all the spusers by looping through all spuser from the sitecollection.

now that the users within the site collection is migrated we should migrate all users in the user profile service DB. if you have more than one site collection, run an outer loop which picks up all site collection and migrate user's within.